(a) Field of the Invention
The present invention relates to an internal rotation type direct motor-drive portable angle grinder with an internal rotation type motor rotating part coaxially and directly driving a grinding wheel. By means of the direct drive, the present invention prevents the emission of noise made by angle type transmission devices; and/or an inertial body is installed on the motor rotating part to form a flywheel to improve the grinding, polishing and machining or cutting abilities of the grinding wheel; and/or a motor is established to be open or semi-hermetic for the space from the interior to a housing and/or a handle of the motor to improve the effect of heat dissipation outward. Aside from a manually controlled electromechanical device, a power storing and discharging device is also installed in the handle for use as a power source.
(b) Description of the Prior Art
Traditional motor-drive right-angle type portable grinder is an electrical tool designed according to ergonomics. Its structural features are the following:
1. The angular difference between the handle axis extending from the housing and the grinding wheel axis is between 30° and 150°;
2. The electric motor is installed in the handle; and
3. An angle type transmission device such as a bevel gear set is present in between the grinding wheel spindle and the motor spindle installed in the handle;
Because the above structure necessitates an angle type transmission device, the resulting very loud noise is the deficiency.